This invention relates to a patterning process using a specific energy-sensitive ladder type organo-siloxane resin and a process for producing electronic devices by utilizing this patterning process. The ladder type organosiloxane resin used in this invention has such a specific property that when it is irradiated with energy rays such as light rays, X-rays, electron beams and ion beams, it is rendered insoluble in a specific solvent, and a film of the insolubilized resin has a high insulating property and heat resistance. Accordingly, after this resin has been used as a material to be etched in the lithographic process, the resin can be used as an insulating layer as it is or after it is heat-treated.
Among polymeric compounds, there are presently resin compositions having such a specific property that when they are irradiated with visible rays, ultraviolet rays, X-rays, electron beams, ion beams and the like, polymerization or decomposition occurs to render them insoluble or soluble in specific solvents. It is well-known that the lithographic process comprising selectively irradiating a thin layer formed of such a resin composition (hereinafter referred to as "resist") with energy rays and selectively dissolving the soluble portion alone in a specific solvent to form a desired pattern is used for the production of semiconductor devices and the like. However, known resists are ordinarily poor in heat resistance and are not completely chemically stable, and furthermore, they are not sufficiently satisfactory as insulating materials. Therefore, there is ordinarily adopted a method in which a pattern formed of such a resist is used as a mask for etching an insulating or conductive material located below the mask of the resist and the resist is removed after completion of the etching operation. In other words, the resist is necessary only as a masking material for the selective etching step and it is not a material to be left as a part of the final product. Accordingly, there would be great advantages in a resist which is excellent in heat resistance and in its insulating property, and if a resist layer, formed by selectively irradiating this resist with energy rays and selectively removing the resist to form a disired pattern, could be used as an insulating layer as it is or after it is subjected to an additional simple treatment. These advantages will be especially prominent in the process for the production of semiconductor devices wherein the etching step is repeated many times, because the process steps are remarkably simplified.
J. C. DuBois et al., in "Polyvinyl Siloxane (PVS), A Highly Sensitive Electron-Beam Resist", Electron and Ion Beam Science and Technology, Fifth International Conference, pages 112-122 (1972), disclose an electron beam-sensitive resist comprising a ladder type organosiloxane resin. The ladder type organosiloxane disclosed has a vinyl group (CH.sub.2 .dbd.CH--) on the side chain and has a relatively low molecular weight. Accordingly, it is considered that this resist is not a highly heat-resistant resist as intended by this invention. The above reference does not teach a process for producing an electronic device by utilizing the above ladder type organosiloxane resin. Although the reference teaches that a resist of the above resin is heated to convert it to an inorganic silica compound, the reference does not suggest at all that the resist will be left as a heat-resistant insulating layer.